Recent years have seen a number of proposals of digital cameras provided with an imaging element, which is a kind of electronic circuit, such as a CCD (charge-coupled device), or a CMOS (complementary metal-oxide semiconductor). The digital camera is configured to receive an optical image by an imaging element, and output it after conversion to an electrical image signal, so that image information is recorded to a memory device, such as a built-in memory device or a removable memory card.
In recent years, such digital cameras have increasingly tended to have an imaging element with a higher pixel count and a more compact size. As the pixel count of the imaging element becomes higher, the file size of the image information to be outputted is increased, and therefore a vast memory region is required as compared to conventional memory regions. In addition, such a vast quantity of information is required to be processed in a short period of time, and therefore the circuit scale has been increasing.
In order to house such a circuit with an increased size within a compact body, circuit board integration has been advanced, resulting in a complex structure. On the other hand, there has been some demand to increase the resistance against external shock. For example, Japanese Laid-Open Patent Publication No. 2006-251241 proposes a means for protecting a liquid crystal display panel from external shock by providing a buffering space surrounding a liquid crystal panel, such that the liquid crystal display panel stays out of direct contact with an exterior housing having received external shock.
FIG. 13 illustrates the external appearance of a digital camera with a plurality of circuit boards connected together via a connector. Provided within a camera body CB are a first circuit board 11 and a second circuit board 12, which are connected together via a connector CO. Such a form of connecting a plurality of circuit boards via a connector is common among digital cameras. Note that although not shown in the present example, in some cases, spacers are provided on the circuit board 11 or 12 in order to keep an exterior housing at a predetermined distance from the circuit board 11 or 12, or keep a predetermined distance between the circuit boards 11 and 12.
FIG. 14A illustrates the configuration of the connector CO. The connector CO is composed of a male connector 2 and a female connector 3. The male connector 2 has a plurality of female metal fittings (not shown) contained at the front side (the bottom side in the figure) of a housing 21. Attached at the back side (the top side in the figure) of the housing 21 are a plurality of electric conductors 22 connected to the metal fittings. The electric conductors 22 are connected by, for example, soldering to wiring formed on the circuit board.
On the other hand, the female connector 3 has a plurality of pins (not shown) disposed at the front side (the top side in the figure) of the housing 31, which are connected to the female metal fittings of the male connector 2. Attached to the back side (the bottom side in the figure) of the female connector 3 are a plurality of electric conductors 32 connected to the pins.
FIG. 14B illustrates the male connector 2 inserted into the female connector 31 viewed from the direction indicated by arrow A in FIG. 14A. This figure shows a cross section of the female connector 3 (the housing 31), and an end surface of the male connector 2. Note that for convenience of drawing, the electric conductors 22 and 32 are simplified. As such, the housing 21 of the male connector 2 is inserted into the female connector 3, so that the female metal fittings of the male connector 2 are appropriately engaged with the pins of the female connector 3 to achieve a reliable electrical connection between the connectors.
FIG. 15 illustrates the two circuit boards 11 and 12 disposed in the camera body CB, which are connected by the connector CO in such a manner as to be appropriately engaged with each other as shown in FIG. 14B. The interior of the camera body CB is partitioned by a frame 4 into a circuit room Rc on the top side and a battery room Rb on the bottom side. Disposed in the circuit room Rc is the connector CO having the male connector 2 inserted into the female connector 3, while disposed in the battery room Rb is a battery 7.
The frame 4 is enclosed in the exterior housing (an external cover 5 and a battery lid 6). The external cover 5 is secured to the frame 4. Furthermore, the battery lid 6 is detachably attached to the external cover 5.
The female connector 3 is disposed on the first circuit board 11, and the male connector 2 is disposed on the second circuit board 12. The first circuit board 11 is electrically and mechanically connected to the second circuit board 12 by the male connector 2 inserted into the female connector 3.
In the case of electronic devices such as digital cameras, it is common that a plurality of circuit boards are connected together by a connector, and contained in an exterior housing so as to keep a predetermined distance from the exterior housing, as described above. When a strong external force or shock is applied to the camera body thus configured, the exterior housing might be distorted, and in some cases, the distortion might be more than expected. In such cases, the distorted exterior housing is brought into contact with the circuit board, so that the strong force is directly transmitted to the circuit board.
FIG. 16 illustrates an example where an external force is transmitted to the circuit boards from the exterior housing distorted by the external force in the camera body CB as shown in FIG. 15. In FIG. 16, the exterior housing (in this figure, the battery lid 6) is first distorted by the external force applied in the direction indicated by arrow F (hereinafter, referred to as the “direction F”). Then, the battery lid 6 is distorted and brought into contact with the frame 4, thereby distorting the frame 4. As the frame 4 is distorted, it is brought into contact with an end of the second circuit board 12, so that the external force tends to cause the second circuit board 12 to move in the direction F.
The external force, which has been applied to the second circuit board 12 by the frame 4, is transmitted to the first circuit board 11 via the connector CO (the male connector 2 and the female connector 3). Since the first circuit board 11 is secured to the frame 4, it resists the external force, and makes no movement. However, the second circuit board 12 is not secured to either the frame 4 or the exterior housing, and therefore cannot resist the external force, so that it tends to move in the direction F. Also, the male connector 2 tends to move in the direction F, along with the secured second circuit board 12.
On the other hand, the female connector 3, along with the secured first circuit board 11, tends to maintain its position by resisting the external force. Specifically, stresses acting in opposite directions are generated in the male connector 2 and the female connector 3 of the connector CO that connects the first circuit board 11 and the second circuit board 12 together. Among the first circuit board 11, the second circuit board 12, and the connector CO (the male connector 2 and the female connector 3), the female connector 3 has the weakest mechanical strength, and therefore its housing 31 is distorted or broken at a portion 31d failing to resist the external force. As a result of the distortion or breakage of the housing 31, the male connector 2 secured to the second circuit board 12 moves relative to the female connector 3 in the direction F. On the other hand, a gap G is created between the female connector 3 and a portion 31c of the housing that is opposite to the distorted portion 31d when viewed in the direction F.
Thus, the relative position between the male connector 2 and the female connector 3 is changed, and the pins in the female connector 3 are displaced. Specifically, the female metal fittings of the male connector 2 are disengaged from the pins of the female connector 3. Furthermore, the female connector 3 cannot stably hold the male connector 2 due to the distorted/broken portion 31d and the gapped portion 31c of the housing 31.
The foregoing has been described by taking as an example the problem that occurs to the circuit boards housed in the camera body CB after the camera is completely assembled as an electronic device. However, such a problem where the connection of the connector CO is damaged by a force applied to the circuit boards might be caused in the course of connecting the circuit boards at factories or suchlike. For example, workers have to join the first board 11 and the second board 12 together under the situations where the connection between the male connector 2 and the female connector 3 cannot be directly viewed. Specifically, the workers have to work relying on their own experience and instinct, and when an unnecessary force is applied to the connector CO during assembly of the camera body CB, so that the male connector 2 is displaced with respect to the female connector 3, if they attempt to join the first circuit board 11 and the second circuit board 12 together, the problem as described above might be caused. The same can be said of even the case of production equipment or suchlike, which is used to replace the workers.